How to Make Feminized Seeds at Home
First of all, what are “feminized” marijuana seeds? Although male and female plants look the same when young, only female cannabis plants make buds. Male cannabis plants grow non-potent pollen sacs instead. Male plants also lower yields and cause seedy buds if they’re left among your female plants for too long. Because male plants don’t make buds and their presence reduces the quality of buds, most growers toss male plants the moment they see pollen sacs forming. However, since about half of regular cannabis seeds end up being male, that means you end up tossing half your plants once they start flowering.
Feminized seeds come from two female plants being bred together, causing all offspring to be female (which means every plant makes buds)
While regular seeds make female plants about half the time, feminized seeds only create female plants. That means you won’t need to toss half the plants once they start flowering. But how are feminized seeds made and can you make them at home?
Feminized seeds are created by breeding two female plants together. Because there are no male parents, all the resulting seeds end up being bud-bearing female plants. With feminized seeds, you can count on every plant to produce buds. Learn more about male vs female plants and feminized cannabis seeds.
Feminized seeds are available from seed banks for nearly every popular or famous strain. Breeders understand that a lot of people just want to grow plants for buds, and don’t care about making a robust breeding program (which is one of the main reasons growers want male plants).
You can’t see the difference between male and female plants until they start flowering (unless you do a genetic test). Feminized seeds ensure all plants are female so you don’t need to worry about it. You know that every plant is female from germination.
So how do seed banks feminize their seeds? How do you breed two female plants together?
The main idea is to force a female plant to produce pollen sacs like a male plant. These flowers (growing on a female plant) create pollen, which can be harvested and used to pollinate another female cannabis plant. The resulting seeds will all end up being female. Can feminizing seeds cause hermaphrodite plants?
Growers can force a female plant to make pollen sacs, and the “feminized” pollen produced can be used to fertilize another female plant. The resulting seeds will only produce female plants.
How do you force a female plant to make pollen?
There are two main ways to make feminized pollen:
- Induce feminized pollen chemically (Recommended) – This is the professional way to feminize seeds and is how reputable seed banks and breeders create feminized seeds to sell to the public. Substances that interact with plant processes such as colloidal silver or gibberellic acid are applied to bud sites of a female plant when they start flowering. Bud sites are drenched daily for the first 3-4 weeks after the switch to 12/12. This causes a female plant to produce pollen sacs which release feminized pollen when they open up. This pollen is used on another female plant to produce feminized seeds. This article will give you step-by-step instructions on how to feminize cannabis seeds using this method.
- Rhodelization (Not Recommended!) – In some cases, a female cannabis plant may naturally start making male pollen sacs or bananas, which can self-pollinate the plant. This happens if the plant is stressed, or if the plant is not harvested in time and buds start to die of old age. The plant is basically doing everything it can to make seeds and save the next generation. This method is “natural” and these seeds end up being mostly female. The problem with this method is you’re selecting for plants that naturally turn into hermies (grow both male and female sex organs) without any chemical induction. This means the resulting seeds are much more likely to turn hermie in natural conditions, too. That’s a problem if you don’t want seedy buds every time you harvest. For that reason, it’s highly recommended you don’t feminize seeds this way. It’s also a good idea to toss any and all seeds that are the result of natural herming (for example seeds you find in your buds even though you didn’t grow any male plants).
Read this article for more in-depth discussion about the pros and cons of each method, and how to avoid hermaphrodite plants when producing your own feminized seeds.
Overview: How to Make Feminized Seeds
This is a quick overview of the process, and then I’ll give the full details and steps below.
1.) Buy or Make Colloidal Silver – The article below will teach you how to make colloidal silver at home, as well as show you where to buy it if you don’t want to make it (it’s actually pretty cheap). It’s basically a solution of silver suspended in water and is available online and in health stores as a dietary supplement.
What about gibberellic acid? From what I understand it can be used exactly the same way as colloidal silver to induce female plants to produce pollen, but I don’t know the recipe for an effective gibberellic acid solution. On the other hand, I know that this exact colloidal silver method works for making feminized seeds. That’s why I’ve only included instructions for colloidal silver. If you’ve used gibberellic acid to make feminized seeds; we’d love to hear from you.
2.) Spray the bud sites of your known female plant daily during the first 3-4 weeks of the flowering stage (until pollen sacs form and start splitting open) – After switching to a 12/12 light schedule to initiate the flowering stage, choose bud sites on your known female plant, and spray/drench them daily with colloidal silver (or gibberellic acid). As the treated flowers develop, they will form into male pollen sacs instead of regular buds. Untreated bud sites on the plant will form into female buds as usual; however, these buds are unsafe to smoke unless you’ve been very careful to make sure they didn’t come into contact with colloidal silver or gibberellic acid during the feminization process as these are unsafe for smoking.
3.) Harvest “Feminized” Pollen – When pollen sacs are ready to be harvested they swell like a balloon and start to open up. Don’t harvest early! Keep spraying the bud sites daily until pollen sacs open or you might end up with empty pollen sacs. When the pollen sacs are ready, the leaf section protecting the pollen will start to crack. At this point, it’s time to collect the feminized pollen. One of the easiest ways to do this is to collect the pollen sacs directly and let them dry for a week. At that point, they can be placed in a bag and shaken to collect all the pollen.
4.) Pollinate Another Female Plant – At this point, take the feminized pollen you’ve collected and use it to pollinate a female plant that has been flowering for about 2-3 weeks (full detailed instructions with a video on how to do this below). Although it’s possible to pollinate the same plant as the original, it’s not recommended in part because the timing doesn’t match up (pollinating buds late in the flowering stage doesn’t produce many seeds). It’s best to pollinate a different female plant that you started budding a few weeks after the original. This increases the number of seeds produced as well as gives the new female plant enough time to develop them to maturity. It also increases genetic diversity compared to self-pollination.
5.) Wait ~6 Weeks After Pollination to Harvest Seeds – After about 6 weeks from pollination, the calyxes on the buds of your female plant will be swollen and fat. You know it’s time to harvest your seeds when they start bursting out. At this point, it’s time to congratulate yourself because you’ve got feminized seeds!
Now that you’ve gotten the overview, here’s the feminization process with detailed step-by-step instructions…
Step-By-Step Instructions (with pics!)
1.) Buy or Make Colloidal Silver (or Gibberellic Acid)
Where to get Colloidal Silver (your options):
Buy Ready-To-Use Colloidal Silver: Colloidal silver is sometimes used as a dietary supplement, so it’s relatively easy to find (never take it without talking to a doctor first though!). If you’re purchasing colloidal silver, try to find a solution that has at least 30 PPM (parts per million) of silver or higher.
- Buy A Colloidal Silver Generator Kit: If you plan on feminizing a lot of seeds, you may want to invest in a generator kit so you can easily make your own endless supply of colloidal silver. This is cheaper in the long run compared to buying it ready-to-use.
- Make Your Own: You can make your own colloidal silver generator at home. The following diagram illustrates what you need to do.
Note: You can purchase gibberellic acid online (a gibberellic acid solution can be used the same way as colloidal silver for feminizing seeds). However, I do not have experience with the gibberellic acid method and don’t know the best way to prepare the solution.
2.) Spray the bud sites of your known female plant daily during the first 3-4 weeks of the flowering stage (until pollen sacs form and start splitting open)
Wait until your plant is 5-6 weeks old before initiating the flowering stage. Some young plants seem to have trouble (and take much longer) to go through the feminization process, and their pollen may not be as fertile, so start with a more mature plant.
When plants are ready, change to a 12/12 light schedule to initiate flower formation and put cannabis plants in the flowering stage. Note: If you’re feminizing an auto-flowering plant, start spraying daily when the plant is about 20 days old from seed. This is when most auto-flowering cannabis strains start making flowers.
As soon as you change the light schedule (and maybe even a day or two before) start spraying your plants thoroughly with colloidal silver at every bud site you want to form into pollen sacs.
Spray bud sites thoroughly, drenching them with colloidal silver every single day. Bud sites are located wherever leaves meet stems.
The above pic shows you where pollen sacs form on the plant (the same places female buds form).
Important! Keep spraying daily until pollen sacs open up. Don’t stop spraying early, even if pollen sacs appear to be already formed, otherwise they may not produce much pollen
A spray bottle / mister is really helpful for spraying bud sites evenly and thoroughly
You can choose to treat a single bud site or all the bud sites on the plant. Any untreated bud sites will develop into female buds as usual. If you want to smoke these buds, it’s incredibly important to avoid letting them come into contact with colloidal silver because silver is not safe to smoke. (Don’t worry, feminized seeds don’t contain any silver). I highly recommend letting the whole plant be your test subject so you don’t have to worry about that
3.) Harvest Your Feminized Pollen
When pollen sacs are starting to crack and look like they’re about to open up (or if you can see one has already opened) then your pollen is ready for harvest!
When pollen sacs are cracking and opening up, you’re ready to harvest your pollen!
Pollen spilling onto a nearby leaf
One way to harvest your pollen is to gently and carefully remove all the pollen sacs. Let them dry in open air for a week, and then put them in a resealable bag. If you shake the bag the pollen should easily spill out. You may need to cut a few open yourself.
How to Store Feminized Pollen: Moisture is your main enemy when storing pollen. It can help to double the mass of the pollen collected by adding regular cooking flour. This absorbs moisture during storage and as an added bonus, it increases the volume to make application easier when you get to pollinating. If pollen is totally dry and you triple-bag the pollen-flour mixture and stick it in the freezer (with a good nametag so you know where the pollen came from), your pollen can be stored for a year or longer. You can add a few silica packs (which suck out any remaining moisture) in the bag to make extra sure that the pollen stays totally dry.
4.) Pollinate Another Female Plant
When your chosen mother is 2-3 weeks into the flowering stage, take a small paintbrush or powder brush and ‘paint’ your feminized pollen on the developing bud sites you want to pollinate. Bud sites (for both male and female plants) are located wherever you can see leaves meet a stem.
Buds are ready to get pollinated when they look like little bunches of white hairs
Only the buds that come in contact with pollen will grow seeds. You can choose to pollinate all of your buds or just a few on the plant.
Here’s a video by Ed Rosenthal on Youtube showing you how to pollinate buds with pollen. Make sure to touch all the female pistils/hairs with your pollen.
5.) Wait About 6 Weeks Then Harvest Seeds
It usually takes about 6 weeks for your feminized seeds to fully develop. Some plants are literally dying right as the seeds become ready, so to get the most viable seeds, you need to try to keep it alive until the seeds actually start dropping. The seeds can be used right away, or stored in a cool, dry place for a few years. Don’t forget to label them with the date.
This seed is about to burst out of its calyx
This is what it looks like when the seed is exposed
Picture Journal of Making Feminized Pollen with Colloidal Silver
This grower initiated the feminization process on a seedling that was only a few weeks old. As a result, the plant wasn’t able to get big enough to produce many pollen sacs. You will get even better results if you start with a plant that is at least 5 weeks old
October 18 – Plant right before the switch to 12/12
October 27 – After being drenched with colloidal silver daily for a little over a week
October 30 – Pollen sacs are forming
November 15 – Pollen sacs appear to be almost fully formed and are swelling in size, but haven’t opened up yet. Don’t stop spraying colloidal silver or you may end up with empty sacs!
November 27 – Pollen sacs are opening up! Collect the pollen before they’re all open!
FAQs – Frequently Asked Questions
How can I identify plant gender before the plant actually starts flowering?
There are a few ways to identify plant gender before the plant actually starts flowering, and each is helpful in different situations.
- Use feminized seeds – All your plants will be female if you start with pre-made feminized seeds.
- Start with a clone – A clone is an exact copy of another plant. If the “mother” of the clone is a female plant, it means the clone is also female
- Look at preflowers (identify plants when they’re 3-6 weeks from seed) – If you know where to look, cannabis plants will actually reveal their gender in the vegetative stage when they’re just 3-6 weeks from seeds. Male plants usually show their gender by 3-6 weeks and female plants usually show their gender around week 4-8 from seed. Learn how to determine the sex in the veg stage by looking at preflowers.
- Test the leaves of your seedling in a lab – It’s possible to send in a leaf from a young cannabis plant to a specialized testing company, and they will be able to determine the gender as soon as 3 weeks from seed! Although I haven’t used any of these companies and can’t recommend any in particular, here’s a link to one example just so you can see what I’m talking about. From talking to other growers who use this method, it appears to be accurate.
- Take a clone and force it to start flowering – if you take a clone from a vegetative plant, you can force that clone to start flowering and reveal its gender. You’ll know the sex of the “parent” plant by the sex expressed by the clone. This is what I do to determine the sex. I cut off a piece of the plant, stick it in a glass of water (don’t forget to label it with the strain), and give it a 12/12 light schedule until the little piece starts forming either pollen sacs or buds.
The easiest way to identify sex with unknown seedlings? Cut off a small branch of the plant, stick it in a cup of water with a label, and keep it in a sunny window on a 12/12 light schedule until buds or pollen sacs start forming. As long as the plant is getting bright light in the day and long dark nights, it will reveal its sex in just a few weeks (you don’t even need to wait for roots to form).
Can I Make a Breeding Program Using Just Female Plants and Feminized Seeds?
Yes, it’s possible to use just female plants and feminized seeds for further breeding, with one major caveat.
Without careful and thorough testing, it may be possible to accidentally select cannabis plants that tend to herm (make male flowers or pollen) and cause seedy buds when you don’t want them to.
For each possible “mother,” clones should be grown in several different environments and tested thoroughly to make sure that the mother plant does not have any tendency to make pollen naturally in normal or stressful conditions. It’s okay if plants grow pollen sacs if induced chemically since that is very unlikely to happen in someone’s garden on accident, but you don’t want plants that will start growing male flowers on their own without chemical induction. Thorough testing of plant hardiness is always important when breeding, but it may be especially important when breeding feminized seeds together.
Are there other reasons I should avoid breeding seeds without males?
The most common reason growers say you shouldn’t do this is because it’s “unnatural” or doesn’t “seem right.” Some growers say you need male plants for genetic diversity. I’ve also heard growers say that the resulting plants will be weaker, sterile, and less potent. Someone once even told me that resulting plants “will be worse in every way.”
As of yet, I haven’t seen any of these claims backed by actual personal experience, or any real-life examples showing why using feminized seeds is not a viable way to breed new strains.
To those who say this type of reproduction just doesn’t seem right, the evolutionary strategy of plants using only female and hermaphrodite plants to breed is actually pretty common and is known as gynodioecy. One example of a plant that only reproduces this way is a flower found in Canada and the US called Lobelia siphilitica, also known as the Great Lobelia. Obviously, this reproduction method isn’t exactly the same as artificial feminization since the pollen production is caused naturally instead of induced chemically, but examples of gynodioecy show that a female flower-based breeding population can exist in the wild even when no plants are purely male.
The Great Lobelia naturally reproduces using only female and hermaphrodite plants. This is similar to the cannabis feminization process because it results in a population of plants that all primarily grow female flowers, with no pure male plants
When it comes to genetic diversity, the ability to cross out to thousands of different cannabis strains allows you to dramatically increase the gene pool without using male plants. So those are my answers to the common objections of a feminized seed-based breeding program, however I am just a theory-crafter when it comes to this topic. It certainly seems possible that a feminized-only breeding program could run into unforeseen problems down the road, but as far as I know there isn’t any evidence of that so far.
Although I have a few anecdotes from growers who have used only feminized seeds for a few generations, it would be much better to share information from someone who has conducted plenty of testing over several generations. We’d love to hear from you if you have bred more than a few generations using only feminized seeds and want to share your experience.
What are the positive aspects of breeding two feminized seeds together?
Besides not having to worry about male plants in the next generation, the main advantage of doing this is you have a much better idea of what you’re working with when it comes to producing the type of buds you’re looking for. When you’re growing a male plant, it has several genes it will pass to its offspring that has to do with how buds develop, but since it’s a male plant those genes aren’t expressed and it’s hard to figure out what they are.
Historically, the way to learn more about the “hidden genes” contained in a male plant is to breed it to several well-known female plants and see how the offspring compare to each other. The genes that don’t come from the known mother plant are assumed to come from the male. Another way of going about this is to take several clones of the same well-known female plant and breed them with many different male plants to see which ones produce the best offspring.
After testing with several pairings, you start to get an idea of the hidden genes a male plant has to offer to its female offspring. This time-consuming process of documenting and identifying good male plants is why proven stud male plants are one of the most valuable and closely guarded types of clones available today.
But the process of finding the right “father” is a little different when you start with two female plants. In this case, you already know quite a bit about the genes of both parents because you can just look at and test the buds of both plants directly. This allows you to pinpoint desirable genes with less guessing and much less time spent growing out and cataloging plants.
Breeding two female plants together offer hints about what kind of buds their genes will produce
Why even have male plants then?
In nature, male plants are effective at increasing genetic diversity by ensuring cross-pollination. With only purely male and purely female plants, every resulting seed will have two different parents.
Another big advantage in the wild of having separate female and male plants is sexual specialization. In other words, plants are able to evolve male and female traits separately, so each type of flower can become more specialized at its unique “job.”
However, this isn’t the only successful breeding strategy for plants. In fact, only 6-7% of plants have completely separate male and female plants like cannabis plants do (known as dioecious plants). Most plants grow some mix of male and female flowers on each plant, with different combinations offering different evolutionary benefits.
You might enjoy this scientific article if you want to learn more about the evolution of sex determination in plants and animals: Sex Determination: Why So Many Ways of Doing It?
And although most cannabis strains (at least the good ones) display either purely male or purely female flowers, there are some wild populations (and some strains of hemp) that regularly produce plants with male and female parts on the same plant.
When it comes to artificial selection for breeding new strains, the grower is in charge of cross-pollination, so there’s no need for the plant to specialize in male parts. Pretty much the only thing most growers care about is how female flowers develop. So (unlike in nature) growers have the freedom to choose plants that improve female buds without even having to consider how it might affect male plants.
Only a small percentage of plant species produce male plants like cannabis.
Can feminizing seeds result in hermaphrodite plants?
The answer is yes. If you do it the wrong way then feminization can lead to plants with an increased chance of herming. However, with a well-tested and well-bred feminization program, one of the main goals is to breed out any plants with hermaphroditic tendencies that show up under normal conditions. When you buy feminized seeds from trustworthy breeders, you can count on the fact that every plant will end up growing only female flowers and that’s it.
This is a relatively big topic with a lot of opposing opinions so I wrote a whole article about it.
Feminizing seeds the wrong way can result in hermaphrodite plants.
Can I pollinate the same plant I collected the pollen from?
Yes, it’s possible. However, it’s not really recommended because, for one, the timing doesn’t match up. By the time your pollen is ready to use, your original plant will already be several weeks past the optimum pollination point. It’s best to pollinate a female plant that has only been flowering about 2-3 weeks, but pollen sacs need more time before pollen is ready to use. It’s also possible to run into unwanted side effects from self-pollination/in-breeding.
One thing to keep in mind is even if you pollinate a plant to itself, the resulting seeds are likely not going to be exact copies of the original (unless the original plant is extremely inbred). The resulting seeds include not just the mother’s expressed genes but also her hidden ones.
How to Feminize Seeds
It’s important to learn how to feminize seeds so you can save time on your grow. When the traditional fertilization methods are used to grow your marijuana plants, you have less control over the gender of future marijuana plants.
That is why many marijuana growers take extra steps so you receive female marijuana plants at the time of harvesting. To do it yourself, feminize seeds prior to your harvest.
What are Feminized Cannabis Seeds?
Feminized cannabis seeds produce only cannabinoid- and trichome-rich flower buds on female cannabis plants. Cannabinoids and terpenes are responsible for the potency, aroma, and flavor of cannabis.
A crop that uses high-quality feminized seeds will produce a female-only crop without the presence of male plants, which can pollinate your crop and potentially reduce your yield.
Another type of seed, a regular seed, is a result of natural pollination and breeding male and female seeds together. Cannabis growers working with regular seeds have a 50% chance of either yielding a female or male marijuana plant. Growing from regular seeds isn’t the best option if you’re looking to strictly grow cannabis buds. While male plants serve their specific purpose to pollinate females, they don’t produce the trichome covered flowers that female plants do.
How Are Feminized Seeds Made?
Feminized cannabis seeds serve a major purpose for commercial and home growers. Feminized seeds can be made by inducing a regular female cannabis plant to grow male sex organs that contain pollen. The hermaphroditic pollen will contain only the female X chromosome and no male Y chromosomes.
When used to pollinate a female cannabis plant, the seeds produced between the two plants will inherit two X chromosomes meaning that all subsequent seeds will be feminized.
The Benefits of Growing Feminized Seeds
Growing feminized cannabis seeds has many benefits over regular seeds. For one, growers don’t have to hedge their bets hoping that the regular seeds will produce female plants. Instead of planting more regular strains than needed to get lucky and get enough females for your specific purpose, you can stick with a sure bet using feminized strains. Using feminized seeds can speed up the growing process by eliminating the need to watch out for male plants, saving you time and space.
Male plants run the risk of pollinating female plants causing them to develop hermaphroditic structures and, ultimately, lower your plants’ yield compared to a grow without male plants. Weeding out the male plants, however, takes time and energy. Male plants display their sexual organs when the photoperiod changes naturally or when indoor lighting environments change.
Growers that don’t want to spend the time monitoring the plant every day can use feminized seeds to ensure that their garden will grow flower buds. Otherwise, growers will have to keep their eyes peeled for male plants and remove them from the grow immediately.
Male vs Female Marijuana Plants
Generally speaking, there is no way that you can determine the difference between male and female marijuana seeds in the initial stages of planting. In addition, you are also not able to change the gender of your marijuana deeds. The concept of having feminized marijuana seeds is to maximize the female seeds that will be part of your marijuana crop. Why would you want female marijuana plants? Well, these are known to have a higher level of THC content. Male plants have reduced THC content and for that reason, female plants take precedence over male plants. With cannabis seed feminization, there are several pollination techniques that the marijuana grower can use for a favorable outcome.
Buying the Right Cannabis Seeds
Female marijuana seeds are sold by various companies. So, you don’t have to wait to get your own. You can use the ones available to you and by doing so, you will be sure that your outcome is a female marijuana plant with more THC content. Be careful when buying marijuana seeds from companies online. Make sure this is a reputable company known for selling and delivering the right female marijuana seeds.
Learn How To Grow Cannabis!
Some “feminized” seeds may produce hermaphrodite plants if the seeds are of low quality. High-quality feminized cannabis seeds from reputable seed banks have been bred to not display hermaphroditic characteristics under optimal growing conditions. If you’re looking for a sure thing, carefully consider your cannabis seed source.
Alternative Methods to Feminizing Weed Plants
If you are going to do the feminization of marijuana seeds yourself, then there are methods that you can use namely:
- Colloidal Silver
- Silver Thiosulfate Solution
Each of these methods should be successful, if used in the right way to produce female marijuana plants. Let’s quickly look at each method briefly.
Pollinating Cannabis Plants
One of the simplest ways to produce feminized cannabis seed is to pollinate your plants yourself. Some cannabis strains can produce male flowers when the colas have reached late ripeness. Side note: Ed Rosenthal, master grower and proud member of the CTU faculty, prefers to harvest plants around this time. Harvest the pollen by using a clean and small painting brush to transfer the pollen into a metal or glass container or in small amounts directly on the flowers.
Some outdoor-friendly cannabis strains may become stressed when grown in indoor environments, which can increase the chance of producing hermaphrodite flowers. Indoor growing environments can stress plants with fluctuating light cycles and heat. Stress training techniques are difficult to pull off, even for experienced cannabis growers. If you do happen to spot a hermaphrodite with pollen, collect the pollen and save it for later use when you feel comfortable using it.
Using Chemicals To Feminize Seeds
Large-scale and home growers have harnessed the power of certain chemicals that can induce male flowers in female marijuana plants. These chemicals are used to hinder ethylene production. Ethylene is a plant hormone that helps cannabis plants ripen and produce female flowers. When ethylene production is stalled, female flowers aren’t produced. Keep in mind, these chemicals must be directly applied to each branch that you want male flowers to grow.
The Silver Thiosulfate Method
The Silver Thiosulfate Solution, also known as STS, is one of the most common methods of generating female marijuana seeds. It is very effective in allowing female marijuana seeds to be available to marijuana growers. Using this method will feminize the seeds in the best way possible, making more available on the market for growers. The solution is made of a combined silver nitrate and sodium thiosulfate. The solution result is a hormonal response to stress found in the marijuana plant. Because of this, gender change is triggered.
You can do all of this yourself, but the marijuana plants have to be wisely chosen. You should only take female plants from a single cannabis strain that is almost mature. Then you would separate the plant from the bunch and spray the plant with STS. Allow it to dry and then replace it, making sure it sits alongside the other plants in the bunch.
There are over 300,000 jobs in the cannabis industry. CTU trained me for one of them!
How to make feminised cannabis seeds
Until the 1990s, any cannabis cultivator was aware that, at some point, they had to separate the male and female plants if they didn’t want the first ones to pollinate the latter, which results in plants completely full of seeds. However, those were the days when pioneering seed banks like Dutch Passion were revolutionizing the cannabis scene with the birth of the first feminized cannabis strains, or in other words, seeds that only develop into female plants. At the beginning of the 20th century, many seeds banks were offering this type of seeds, feminized versions of classics strains that had been cultivated during many years as regular plants.
We are sure that by now you’d probably have grown some feminized seeds, maybe even though you are a purist and the fiercest defender of regular seeds. But. do you know where feminized seeds come from? Are you familiar with the processes used by both breeders and growers to obtain them? In this article we explain everything!
Feminized cannabis seeds quality control
Advantages of growing feminised seeds
Indeed, the advent of feminized seeds brought about a genuine revolution within the cannabis sector. Growers were now sure that all their plants would be females, without the need to differentiate between male and female plants or having to remove the males before they could ruin the crops, which offers a number of benefits of significant importance:
- Space and resources saving: no more growing plants which eventually will be removed for being males.
- Reliability: it’s not that most plants are female, or that they are genetically more likely to produce female plants. The plants grown from feminized seeds have only female chromosomes (XX), therefore this method is 99% reliable.
- Sinsemilla plants: by not having males in the grow room, your female plants won’t be pollinated, so they won’t produce any seeds during the flowering period (something that every cultivator wants, unless they want to obtain seeds)
These advantages were of great interest for the growers, and soon feminised seeds accounted for a large portion of the seeds available in the market. In addition, being able to use only female plants (generally known and selected clones) to produce seeds had another great advantage for seed producers and breeders of new varieties: they no longer need to keep males in their gene pools! And not only that. from that moment on, any female plant they could get their hands on could be used as a male to pollinate other plants, thus exponentially increasing the possibilities of creating new crosses.
Outstanding Orange Candy feminised from Philosopher Seeds
It is not surprising, therefore, that at present, feminized seeds represent virtually all the seeds in the market, since they offer a number of significant advantages for both professional and home growers and breeders, for photoperiod and autoflowering plants. The main disadvantage of this method is a well known and hotly debated issue: the growers who buy this type of seeds cannot produce their own seeds in the absence of male plants, so the only way they can manage it it’s using the same process to obtain this type of seeds. But. what are these processes and what are they based on?
Female crosses: feminised cannabis seeds are born
As we’ve already mentioned, feminized seeds are the result of a process that reverses the sex of a female plant, that is, she is forced to produce male flowers. This way, and once into flowering, the female chosen will start to develop what we know as male flowers (stamens and anthers), which, just like male plants, will release the pollen that will pollinate the female plants. What is then the difference between a male plant and a reverted female plant?
The sex of cannabis plants is determined in the same way as ours, through the so-called sex chromosomes or genosomes. Male plants have a couple of different sex chromosomes called “XY” or heterogametic, while female plants have two chromosomes called “XX” or homogametic. When crossing a male (XY) with a female (XX), we will obtain around half of the plants of each type in their offspring. In other words, when a breeder uses a male and a female plant, the seeds produced by them will be approximately 50% males and 50% females.
After this explanation, many of you will have already figured out that if we cross two female plants (reversing the sex of one of them to force it to produce pollen), the result will be seeds that will produce female plants, as there are only female sex chromosomes in the equation. If crossing XY with XX produced 50% of each class (male and female), crossing XX with XX will produce plants that only exhibit chromosomes XX, that is to say, female plants. No matter how many times we “transform” a female plant into a male plant, we won´t be changing their genetic composition, which will still be female or XX. This way, the pollen produced by this plant will pass down female sex chromosomes exclusively.
Feminised seeds grown indoors, 100% female plants
As you can see, and although we normally use the expression “reversing the plant sex“, that is not exactly what is done, because the sex chromosomes of the female plant (XX) have not changed, even if we managed to produce male flowers. This “sex change” of female plants can be achieved in a number of ways, but usually with the same goal: to reduce the level of ethylene in plant tissues and/or inhibit the ethylene action, which makes the plant develop male flowers on entering the flowering period, as if it were a male from regular seeds. This is because ethylene is a natural regulator of the sex expression in plants!
Let’s see now the most popular ways to reverse the sex of a female plant in order to produce feminized seeds.
Methods used to produce feminized cannabis seeds
There are several ways to secure that a female plant produces pollen, and almost all of them require some type of chemical that is often sprayed on the plant. Once sprinkled with the chosen product and under a flowering photoperiod, the plant will flower normally, but as a male instead of female, producing ‘feminized’ pollen (which only contains chromosomes XX) that can be used to pollinate other females in order to produce seeds. These are some of the most commonly used techniques:
Stress or rodelization
One of the first methods used to obtain seeds that produce female plants was stress or rodelization. There are several ways to stress the cannabis plants to make sure they develop male flowers, such as through temperature, nutrition, photoperiod, and pH. However, supporters of this technique often prefer something as simple as delaying the harvest 2-3 weeks in order to force the plants to develop a few male flowers without stressing them as much as with any of the other methods we have mentioned.
Although this action will produce far less pollen than other techniques like STS, it will be enough to obtain a handful of seeds for the domestic growers to try to create their own feminized crosses. Also, the great advantage of this technique is that is 100% natural, and it doesn´t use any chemicals. It is an excellent alternative for anyone who just wants a few seeds and wishes to keep it simple without any formulas or laboratory products. However, bear in mind that this is the only method listed in this post that may produce some plants with hermaphroditic traits.
Male flower produced by rodelization
STS or silver thiosulfate solution
Without any doubt, one of the most commonly used methods for both producers and seed banks. This is a solution made of distilled water, silver nitrate and sodium thiosulphate (sometimes called sodium hyposulphite) that, after being sprayed on the female plants, inhibits their ethylene action resulting in the formation of male flowers once flowering has been induced. STS is relatively easy to prepare, although its lifespan after combining the two components is quite limited, barely a few days as long as it´s well preserved (in a dark and cool place).
It is important to mention that you must not consume any part of the plants sprayed with this type of product, although that would be weird, as the plants have “become” males and won´t produce any buds. Nevertheless, you shouldn’t use the reverted plants to make resin extracts; the best thing is to discard them after harvesting the pollen. Both components, sodium thiosulphate and silver nitrate, are also used for photo-development.
This is another way to revert the sex of the plants, but this time using a solution made of 30ppm colloidal silver (that you can easily find in many pharmacies and also online) and distilled water. The solution must be applied for a few days until the plant starts producing male flowers, something that it´s not necessary with STS, where in most cases one single application is enough.
Colloidal silver is formed by electrically charged silver nanoparticles and has antibacterial and antifungal properties. This product was introduced in the market in 1980 for therapeutic use. However, as with STS, you should get rid of the sprayed plants once their pollen is harvested, as colloidal silver is absorbed systemically by the plant and remains in its tissues.
This sativa plant treated with STS started flowering as a female but soon developed male flowers
This is a method researched by Mohan Ram, who also conducted extensive investigations on plant sex reversal with STS. According to his findings, sodium thiosulphate (STS) is more effective in producing male flowers and viable pollen in female plants. Probably because of this, silver nitrate is mixed with sodium thiosulphate, instead of using it in isolation.
Gibberellins are plant hormones that help regulate various processes related to the development of the plants. There are several types of gibberellins available in the market, although the most common and effective is gibberellic acid or GA3 (Gibberellin GA3). This product is used in a very similar way to colloidal silver, sprayed on the plants during several days before switching the photoperiod over to flowering.
It is worth stating that one of the side effects of gibberellic acid is a significant stretching of the treated parts of the plant, so don’t be surprised if this happens to your plants! The recommended dose to achieve the best results is approximately 100ppm.
Urban legends and lies about feminized seeds
Despite the fact that, after two decades of cannabis cultivation, many of the false myths surrounding feminized seeds have been debunked, from time to time we still hear some arguments like the ones shown below. As is often the case, many of these stories are spread by people who have never grown this type of seeds or have none or very limited experience with them. Ignorance is always a bad thing, and that’s why we want to emphasize several points in relation to feminized seeds and the myths that often go with them; myths such as the following:
Feminized seeds produce hermaphrodite plants:
The problem with monoecious hermaphrodite plants has more to do with the parents used (and if they exhibit any hermaphrodite trait) rather than with the type of seeds produced. If to create a feminized seed you use a female plant with a tendency to produce male flowers, part of its offspring will likely inherit that characteristic, whether the said female plant is used as a pollen donor (after reversing its sex) or as a recipient of pollen (letting it flowering as usual). Yet the same thing happens when producing regular seeds: if the male or female parents are not stable in this respect, neither will be their offspring (or at least part of it).
Marijuana and hermaphroditism
Many growers have been surprised by the presence of hermaphrodite plants in their marijuana crops. In this post we will tell you how to detect them and how to proceed if you find a hermaphrodite cannabis plant in your growing space. We will also discuss the causes of this hermaphroditism.
Feminized seeds produce mutant plants:
Nothing could be further from the truth. It is true that sometimes some plants develop weird traits or mutations, although this also happens with regular seeds. Unfortunately, there seems to be not enough studies comparing the ratio of specimens with mutations of one or other type of seeds; however, given the millions of feminized seeds that have been germinated in the last 20 years, if mutations would pose a problem, the quantity of feminized seeds sold would certainly not be so high, and this would be a “public security” issue within the cannabis sector, both for the growers and the producers of the seeds.
Feminized seeds have chemicals:
This is another lie that some people believe. As it’s been mentioned before, a female plant is sprayed with some chemicals in order to inhibit its ethylene action. After a few weeks of this and once in the flowering period, the plant will produce male flowers and pollen, which will be harvested to pollinate the female plants designated to produce seeds. Once the seeds are formed, they are collected and packed immediately, so they don’t come into contact with any chemicals or the plants that produce seeds, nor, of course, with the seeds themselves. Also, to produce cannabis seeds, you normally need two separated indoor cultivation areas, one for the reverted plants (treated females) and the other for the females to be fertilized to produce the seeds, so the latter can’t get “contaminated” with any chemicals.
Feminized seeds are GMOs:
Once again, this is a false statement. We have already pointed out that by using these sex reversal techniques we inhibit the ethylene action in the female plant, and under no circumstances the seeds (or plants) are genetically modified. The sex chromosomes of the female plant converted into a male plant are still female (XX), nothing has changed at a genetic level.
We hope you found this article interesting; even today, many people are still unaware of the intriguing process behind this type of cannabis seeds. Do not hesitate to leave your comments; we will be delighted to answer them.
- Marijuana Botany, Robert C. Clarke
- The Cannabis breeder’s Bible, Greg Green
- The Cannabis grow Bible, Greg Green
- Breed your own vegetable varieties, Carol Deppe
- Induction of Fertile Male Flowers in Genetically Female Cannabis sativa Plants by Silver Nitrate and Silver Thiosulphate Anionic Complex, Mohan Ram, Sett R.
The articles published by Alchimiaweb, S.L. are reserved for adult clients only. We would like to remind our customers that cannabis seeds are not listed in the European Community catalogue. They are products intended for genetic conservation and collecting, in no case for cultivation. In some countries it is strictly forbidden to germinate cannabis seeds, other than those authorised by the European Union. We recommend our customers not to infringe the law in any way, we are not responsible for their use.